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(No Model.) F. L. BARTLETT'. PROCESS 0F RBFINING PUME.

No. 480,686. Patented Aug. 9, 1892.

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UNITED STATES PATENT OEEICE.

FRANK L. BARTLETT, OF PORTLAND, MAINE, ASSIGNOR TO THE AMERICAN ZINCLEAD COMPANY, OF SAME PLACE.

PROCESS OF REFINING FUME.

SPECIFICATION forming part of Letters Patent No. 480,686, dated August9, 1892. Application iiled Tune 16, 1890. Serial No. 355,622. (Nomodel.)

.T aZZ whom it may concern.-

Be it known that I, FRANK L. BARTLETT, al citizen of the United States,residing at Portland, in the county of Cumberland and State of Maine,have invented certain new and useful Improvements in Process of ReningFume; and I do hereby declare the following to be a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

My invention relates to the manufacture of paint-pigment from low-gradezinc ores and to the refining of impure sublimed fume of zinc and lead;and the invention relates particularly to an improvement in the processof refining fume described and claimed in Letters Patent No. 406,868,granted to me July 16, 1889. The process of reiining set forth in 2osaid Letters Patent consisted in passing the fume to be refined througha heated tube in the presence of air and continually stirring andscraping it from the walls of said tube during its passage through thesame. In the process described air was admitted at one end of the tubeand allowed to flow through it from one end to the other, acting as itpassed along on all the particles of the fume. The effect of thisprocess on fume containing sulphur compounds, carbonaceous matters,volatile metals, as arsenic, cadmium selenium, dac., acids, &c., was towhiten and condense it, at the same time freeing it from all foreignsubstances and leaving it in the form of a pure compound of lead, zinc,sulphur, and oxygen, which analysis shows to contain zinc oxide andoxysulphate of lead. In practical operation the process described insaid Letters Patent gave satisfactory results and produced a pigmentwhich approached to pure white lead in whitness and body; but I havediscovered since making application for said Letters Patent that if theair is excluded from the heated tube and the roasting process allowed tocontinue in an atmosphere ofl sulphurous gas, which is given off fromthe fume in its passage through the tube or by admission ofsulphurous-acid gas from any convenient outside source, the resultingproduct is rendered much Whiter, denser, and more perfect.

In the accompanying drawings I show an apparatus designed to carry myimproved process into effect.

Figure l represents' a part elevation and part longitudinal section, andFig. 2 is an end 55 vlew.

A represents a furnace having a hearth I at one end. A chamber or iiueconnecting with the hearth leads horizontally from one end of thefurnace to the other. A chimney- 6o ilue b leads from the chamberB atthe end of the furnace opposite the hearth. Suspended longitudinally inthe chamber B is a tube C, preferably of cast -iron, its ends extendingthrough the end Walls a of the furnace. There is a free spacesurrounding the tube, so that the hot gases may circulate freely aroundit. Leading from the end where the fume is fed in is an outlet-pipecforcarrying off the gases which come from the heated fume. Extend- 7o ingthrough the tube and fitting it loosely, except at the lower side whenit iits accurately, is a coreless helical screw D. This screw is made ofcast-iron and has strengthening-bars d, cast with the screw andextending longitudinally through it. Connecting with the feed end of thescrew is a hopper E where the fume is fed in,and the screw continuesalong the bottom of the hopper and through the open end of the tube.through the end of the tube, it is provided, for the purpose ofexcluding the air as much as possible, with a core e, having as large adiameter as the thread of the screw will admit. The outlet end ot' thetube C is closed, except 85 a small opening c just sufficient to allowthe fume to pass as it is fed through by the action of the screw. Thescrew is slowly rotated by the gears F.

In workin g my process I feed the fume to be 9o rened into the hopper E,taking pains to keep the hopper lled above the top of the screw, so thatthe air will be prevented from entering to any extent with the fume. The

screw is slowly rotated and the fume fed slowly through the tube.

A fire of coke or When the screw passes 8o l coal is kept burning in thehearth and the tube becomes heated throughout its entire length to atemperature preferably less than 1,000 Fahrenheit. The fume as it passesthrough the tube is gently stirred and turned over and over, so thateach particle receives the same degree of heat, the fume which adheresto the walls of thetube being kept scraped off by the action of thescrew. The loose sulphur compounds are driven 0E, forming sulphurous gasand oxysulphate of lead, with oxide of zinc incorporated with it in sucha manner as to be inseparable by any mechanical means andfrom which iseliminated all of the impurities mentioned, these latter beingvolatillzed and carried off through the pipe c. The,

refined product falls out in a small stream through the opening in theend of the tube. Care should be taken that this opening is so'externally-heated tube or chamber in the presence of an atmosphere ofsulphurous gas, stirringv said fume and scraping it from the Walls ofsaid tube or chamber during its passage through the same, the air beingexcluded from said tube, substantially as described.

In testimony whereofl affix my signature in presence of two Witnesses.

FRANK L. BARTLETT.

Witnesses:

R. S. BARNES, FRANK F. DENNIS.

